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I am looking for a way to do deduplication for my Virtual Machines, I found a project called OpenDudup. It looks promising, it says it needs fuse as a dependancy. After looking up what fuse is, it left me with another question.

What make a file system is user space different from a file system in kernel space?

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You might want to check out the current state of microkernels, which effectively push as much as possible into userspace. – new123456 Jul 19 '11 at 15:25

File systems in user space advantages:

  • Easier development
  • Nice user friendly package (FUSE) to give you a nice template. You have to worry only about getting the special parts of your file system to work.
  • Usable by non-privileged users.


  • Slower. Sometimes way way way slower.
  • Not good if you want multiple users to use the same file system at the same time.

Sometimes FUSE is the only way to get things to work though, so you're happy enough to live with the speed hit.

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Oh, I just noticed. FUSE runs your file system code in user space. Userspace programming errors take down that program, not the whole system. Kernel space programming errors normally take down the whole system, plus, you don't get user isolation so you have to care a lot about security. – Bruce ONeel Jul 19 '11 at 15:09
Ah I see there is a performance hit? – ianc1215 Jul 19 '11 at 15:12
aand you can't boot off a FUSE FS ;p – Journeyman Geek Jul 19 '11 at 15:14

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